Add a `description` to plugins

[jtpio]

Lumino 2 now supports adding a description to plugins: jupyterlab/lumino#572

Currently most plugins in this repo don't make use of it, for example:

notebook/packages/application-extension/src/index.ts

Lines 499 to 533 in b5133c6

	/**
	* A plugin to display the document title in the browser tab title
	*/
	const tabTitle: JupyterFrontEndPlugin<void> = {
	id: '@jupyter-notebook/application-extension:tab-title',
	autoStart: true,
	requires: [INotebookShell],
	activate: (app: JupyterFrontEnd, shell: INotebookShell) => {
	const setTabTitle = () => {
	const current = shell.currentWidget;
	if (current instanceof ConsolePanel) {
	const update = () => {
	const title =
	current.sessionContext.path || current.sessionContext.name;
	const basename = PathExt.basename(title);
	// Strip the ".ipynb" suffix from filenames for display in tab titles.
	document.title = basename.replace(STRIP_IPYNB, '');
	};
	current.sessionContext.sessionChanged.connect(update);
	update();
	return;
	} else if (current instanceof DocumentWidget) {
	const update = () => {
	const basename = PathExt.basename(current.context.path);
	document.title = basename.replace(STRIP_IPYNB, '');
	};
	current.context.pathChanged.connect(update);
	update();
	}
	};
	shell.currentChanged.connect(setTabTitle);
	setTabTitle();
	},
	};

We should add them to the notebook code base, so it's useful for contributors but also for users at some point: jupyterlab/jupyterlab#14536

[jtpio]

This could be a good task for a new contributor willing to get into the notebook code base.

[Ramyahkay]

I am a beginner contributor and I'd like to work on this issue.